Margarity M, Valcana T, Timiras P S
Mech Ageing Dev. 1985 Feb;29(2):181-9. doi: 10.1016/0047-6374(85)90017-x.
This study examines (a) the effects of aging on plasma thyroid hormone concentration and (b) in vivo binding and cytoplasmic distribution of thyroid hormones as well as the conversion of thyroxine (T4) to triiodothyronine (T3) in liver and cerebral hemispheric tissue. The results show that (a) in male Long-Evans rats aging decreases plasma T4 concentration but does not affect plasma T3 concentration and (b) the in vivo nuclear T3 binding does not change significantly. However, nuclear T3 binding derived from T4 is decreased as a consequence of reduced T4 to T3 conversion in both tissues. The nuclear T4 binding is also depressed, perhaps due to the decrease in the T4 of the protein free cytoplasmic compartment. Aging was also found to change protein free and protein bound cytoplasmic distribution of T4. That is, an increase was observed in protein bound cytoplasmic T4 and a decrease in the protein free cytoplasmic T4 of both tissues. These results indicate an overall alteration in thyroid hormone production and peripheral tissue binding and processing of thyroid hormones with a consequent suboptimal thyroid state with aging.
(a)衰老对血浆甲状腺激素浓度的影响；(b)甲状腺激素在体内的结合情况、在细胞质中的分布，以及甲状腺激素在肝脏和大脑半球组织中由甲状腺素（T4）向三碘甲状腺原氨酸（T3）的转化。结果表明：(a)在雄性Long-Evans大鼠中，衰老会降低血浆T4浓度，但不影响血浆T3浓度；(b)体内核T3结合无显著变化。然而，由于两种组织中T4向T3的转化减少，源自T4的核T3结合减少。核T4结合也受到抑制，这可能是由于游离蛋白细胞质区室中T4减少所致。研究还发现衰老会改变T4在游离蛋白和结合蛋白状态下的细胞质分布。也就是说，在两种组织中，观察到结合蛋白状态的细胞质T4增加，游离蛋白状态的细胞质T4减少。这些结果表明，随着衰老，甲状腺激素的产生、甲状腺激素在周围组织中的结合和加工发生了全面改变，从而导致甲状腺状态欠佳。
